Wednesday, February 4, 2015

Peering into the thousands of frozen layers inside Greenland’s ice sheet is like looking back in time. Each layer provides a record of not only snowfall and melting events, but what the Earth’s climate was like at the dawn of civilization, or during the last ice age, or during an ancient period of warmth similar to the one we are experiencing today.

Using radar data from NASA’s Operation IceBridge, scientists have built the first-ever comprehensive map of the layers deep inside the ice sheet.

Layer by layer, scientists have filled in a new map of the hidden
expanses of Greenland's vast ice sheet, revealing where the island hides
its oldest ice.

The 3D map reveals where areas of ice of different ages are located
across the frozen island.
The research team built the 3D map of Greenland's ice sheet
using data from airborne radar and ice cores.
Radar measurements
revealed the ice's thickness, and was also used to find internal layers
concealed under the surface.
The ice cores provided precisely dated ages
for these different layers at various points around the island.
(The
oldest ice found so far in Greenland's ice cores is about 130,000 years
old.)
Like playing a giant game of connect the dots, the team drew in
the map by linking the ice cores with the internal layers detected by
airborne radar.
The researchers have divided the map into Holocene-period ice (the last
11,700 years), ice from the Ice Age (from 11,700 to 115,000 years ago)
and ice from the Eemian Period (115,000 to 130,000 years ago.)

The biggest surprise revealed by the new map is that more ice from the
Eemian Period ice is in central northern Greenland than scientists knew
existed, said lead study author Joe MacGregor, a glaciologist at the
University of Texas at Austin Institute for Geophysics.
"Figuring out
where this Eemian ice might be has been a challenge," MacGregor told
Live Science. "It would be great to get more of it [through drilling],
so we can understand what the Eemian was like."

Researchers are particularly interested in hunting for Eemian Period
ice because it contains clues to how the ice sheet will respond as the
planet warms today.
The Eemian Period was Earth's most recent warm
spell, when the planet was as warm as it is becoming now.
During this
older warming period, Greenland kept some of its ice.
After the Eemian,
the planet's climate entered a long ice age, during which modern humans
evolved.
"The climate changes
that are occurring today are happening a lot faster than in the Eemian,
but if we can understand what the Eemian was like, than we can
understand where [today's] climate is going," MacGregor said.

This is the first time anyone has assembled a stratigraphic map, one
that shows all of the layers of Greenland's ice sheet, the scientists
said.
The results were published January 16 in the Journal of Geophysical Research: Earth Surface.

"It was a challenging problem and a daunting one, because there was a
lot of data," MacGregor said.
"It had kind of become like cleaning out
your garage after 10 years of ignoring it. You know you might find
something very exciting, but you have to go through the pain of cleaning
it."

The new map will serve as the keystone for several planned research
projects, MacGregor said.
For instance, the structure of the ice layers
can be used to study how fast the ice sheet flows and where it's
melting.
Digging into the history of the ice will also reveal more about
how it formed and help predict the future of the ice sheet as the
climate warms, he added.